Psychrometrics.jl

Installing and Loading Psychrometrics

Psychrometrics can be installed and loaded either from the JuliaHub repository (last released version) or from the maintainer's repository.

Last Released Version

The last version of Psychrometrics can be installed from JuliaHub repository:

using Pkg
Pkg.add("Psychrometrics")
using Psychrometrics

If Psychrometrics is already installed, it can be updated:

using Pkg
Pkg.update("Psychrometrics")
using Psychrometrics

Pre-Release (Under Construction) Version

The pre-release (under construction) version of Psychrometrics can be installed from the maintainer's repository.

using Pkg
Pkg.add(path="https://github.com/aumpierre-unb/Psychrometrics.jl")
using Psychrometrics

Citation of Psychrometrics

You can cite all versions (both released and pre-released), by using 10.5281/zenodo.7493474.

This DOI represents all versions, and will always resolve to the latest one.

For citation of the last released version of Psychrometrics, please check CITATION file at the maintainer's repository.

The Psychrometrics Module for Julia

Psychrometrics provides a set of functions to compute the various variables related to water vapor humid air, providing the following functions:

psychro
humidity
satPress
enthalpy
volume
adiabSat
dewTemp

psychro

psychro computes

the dry bulb temperature,
the wet bulb temperature,
the dew point temperature,
the adiabatic saturation temperature,
the humidity,
the saturation humidity,
the saturation humidity at wet bulb temperature,
the adiabatic saturation humidity,
the specific enthalpy,
the specific volume,
the relative humidity,
the water vapor pressure,
the saturation pressure, the saturation
pressure at wet bulb temperature and
the density

given any two of the following parameters:

the dry bulb temperature,
the wet bulb temperature,
the dew point temperature,
the humidity,
the specific enthalpy,
the specific volume or
the relative humidity,

except for the combination of humidity and dew point temperature, which are not mutually independent. If a different number of parameters is given, execution will be aborted. If fig = true is given, a schematic psychrometric chart is plotted as a graphical representation of the solution.

By default, stages plots a schematic diagram of the solution, fig = true.

If fig = false is given, no plot is shown.

Syntax:

(
    Tdry, # dry bulb temperature
    Twet, # wet bulb temperature
    Tdew, # dew point temperature
    Tadiab, # adiabatic saturation temperature
    W, # humidity
    Wsat, # saturation humidity
    Wsatwet, # saturation humidity at wet bulb temperature
    Wadiab, # adiabatic saturation humidity
    φ, # relative humidity
    h, # specific enthalpy
    v, # specific volume
    pw, # water vapor pressure
    psat, # saturation pressure
    psatwet, # saturation pressure at wet bulb temperature
    ρ # density
    ) = psychro(;
        Tdry::Number=NaN, # dry bulb temperature
        Twet::Number=NaN,  # wet bulb temperature
        Tdew::Number=NaN, # dew bulb temperature
        W::Number=NaN, # absolute humidity
        φ::Number=NaN, # relative humidity
        h::Number=NaN, # specific enthalpy
        v::Number=NaN, # specific volume
        fig::Bool=false # show/ommit chart
        )

Examples:

Compute the dry bulb temperature, the wet bulb temperature, the adiabatic saturation temperature, the humidity, the saturation humidity, the saturation humidity at wet bulb temperature, the adiabatic saturation humidity, the specific enthalpy, the specific volume, the relative humidity, the water vapor pressure, the saturation pressure, the saturation pressure at wet bulb temperature and the density given the dew point temperature is 22 °C and the relative humidity is 29 %.

psychro( # all results ordered in one tuple
    Tdew=22 + 273.15, # dew temperature in K
    φ=0.29, # relative humidity
    fig=true # show plot
    )

or, assigning values to variables:

(
    Tdry, # dry bulb temperature
    Twet, # wet bulb temperature
    Tdew, # dew point temperature
    Tadiab, # adiabatic saturation temperature
    W, # humidity
    Wsat, # saturation humidity
    Wsatwet, # saturation humidity at wet bulb temperature
    Wadiab, # adiabatic saturation humidity
    φ, # relative humidity
    h, # specific enthalpy
    v, # specific volume
    pw, # water vapor pressure
    psat, # saturation pressure
    psatwet, # saturation pressure at wet bulb temperature
    ρ # density
    ) = psychro(
        Tdew=22 + 273.15, # dew temperature in K
        φ=0.29, # relative humidity
        fig=true # show plot
        )

Compute the dry bulb temperature, the wet bulb temperature, the dew point temperature, adiabatic saturation temperature, the dew point temperature the humidity, the saturation humidity, the saturation humidity at wet bulb temperature, the adiabatic saturation humidity, the specific enthalpy, the specific volume, the relative humidity, the water vapor pressure, the saturation pressure, the saturation pressure at wet bulb temperature and the density given the specific enthalpy is 79.5 kJ/kg of dry air and the relative humidity is 29 % and plot a graphical representation of the answer in a schematic psychrometric chart.

psychro(
    h=79.5e3, # specific enthalpy in kJ/kg of dry air
    φ=0.29, # relative humidity
    fig=true # show plot
    )

8.5 cubic meters of humid air at dry bulb temperature of 293 K and wet bulb temperature of 288 K is subjected to two cycles of heating to 323 K followed by adiabatic saturation. Compute the energy and water vapor demands. Assume the amount of dry air is constant.

# The volume of humid air is
V = 8.5;
# The initial condition is
Tdry1 = 293;
Twet1 = 288;
(
    Tdry1, Twet1, Tdew1, Tadiab1,
    W1, Wsat1, Wsatwet1, Wadiab1,
    φ1,
    h1, v1,
    pw1, psat1, psatwet1,
    ρ1
    ) = psychro(Tdry=Tdry1, Twet=Twet1, fig=true)
sleep(3)
# The thermodynamic state after the first heating is
Tdry2 = 323;
W2 = W1;
(
    Tdry2, Twet2, Tdew2, Tadiab2,
    W2, Wsat2, Wsatwet2, Wadiab2,
    φ2,
    h2, v2,
    pw2, psat2, psatwet2,
    ρ2
    ) = psychro(Tdry=Tdry2, W=W2, fig=true)
sleep(3)
# The thermodynamic state the after first adiabatic saturation is
h3 = h2;
Tdry3, W3 = adiabSat(h3, fig=true)
sleep(3)
# The thermodynamic state after the second heating is
Tdry4 = 323;
W4 = W3;
(
    Tdry4, Twet4, Tdew4, Tadiab4,
    W4, Wsat4, Wsatwet4, Wadiab4,
    φ4,
    h4, v4,
    pw4, psat4, psatwet4,
    ρ4
    ) = psychro(Tdry=Tdry4, W=W4, fig=true)
sleep(3)
# The thermodynamic state the after second adiabatic saturation is
h5 = h4;
Tdry5, W5 = adiabSat(h5, fig=true)
sleep(3)
# The energy demand is
(h5 - h1) * (V / v1)
# The water vapor demand is
(W5 - W1) * (V / v1)

humidity

humidity computes the humidity of humid air in given the water vapor pressure and the total pressure. By default, total pressure is assumed to be the atmospheric pressure at sea level.

Syntax:

humidity( # humidity in kg/kg of dry air
    pw::Number, # water vapor pressure in Pa
    p::Number=101325 # total pressure in Pa
    )

Examples:

Compute the humidity of humid air at atmospheric pressure given water vapor pressure is 1 kPa at 1 atm total pressure.

humidity( # humidity in kg/kg of dry air
    1e3 # water vapor pressure in Pa
    )

satPress

satPress computes the saturation pressure of humid air given the dry bulb temperature.

Syntax:

satPress( # saturation pressure in Pa
    Tdry::Number # dry bulb temperature in K
    )

Examples:

Compute the saturation pressure given the dry bulb temperature is 25 °C.

satPress( # saturation pressure in Pa
    25 + 273.15; # dry bulb temperature in K
    )

enthalpy

enthalpy computes the specific enthalpy of humid air given the dry bulb temperature and the humidity.

Syntax:

enthalpy( # specific enthalpy in kJ/kg of dry air
    Tdry::Number, # dry bulb temperature in K
    W::Number # humidity in kg/kg of dry air
    )

Examples:

Compute the specific enthalpy given the dry bulb temperature is 25 °C and the humidity is 7 g/kg of dry air.

enthalpy( # specific enthalpy in J/kg of dry air
    25 + 273.15, # dry bulb temperature in K
    7e-3 # humidity in kg/kg of dry air
    )

volume

volume computes computes the specific volume of humid air given the dry bulb temperature, the humidity in and the total pressure. By default, total pressure is assumed to be the atmospheric pressure at sea level.

Syntax:

volume( # specific enthalpy in J/kg of dry air
    Tdry::Number, # dry bulb temperature in K
    W::Number, # humidity in kg/kg of dry air
    p::Number=101325 # total pressure in Pa
    )

Examples:

Compute the specific volume given the dry bulb temperature is 25 °C and the humidity is 7 g/kg of dry air at 1 atm total pressure.

volume( # specific volume in cu. m/kg of dry air
    25 + 273.15, # dry bulb temperature in K 
    7e-3 # humidity in kg/kg of dry air
    )

adiabSat

adiabSat computes the the adiabatic saturation temperature and the adiabatic saturation humidity given the specific enthalpy. If fig = true is given, a schematic psychrometric chart is plotted as a graphical representation of the solution.

Syntax:

adiabSat( # adiabatic saturation temperature in K
    h::Number; # specific enthalpy in J/kg of dry air
    fig::Bool=false # show plot
    )

Examples:

Compute the the adiabatic saturation temperature and the adiabatic saturation humidity given the specific enthalpy is 82.4 kJ/kg of dry air and plot a graphical representation of the answer in a schematic psychrometric chart.

adiabSat(
    82.4e3, # specific enthalpy in J/kg of dry air
    fig=true # show plot
    )

dewTemp

dewTemp computes the dew point temperature of humid air given the water vapor pressure.

Syntax:

dewTemp( # dew point temperature in K
    pw::Number # water vapor pressure in Pa
    )

Examples:

Compute the dew temperature of humid air given the water vapor pressure is 1 kPa.

dewTemp( # dew temperature in K
    1e3 # water vapor pressure in Pa
    )

Reference

The theory and the adjusted equations used in this package were taken from the first chapter of the 2017 ASHRAE Handbook Fundamentals Systems - International Metric System, published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers.

Acknowledgements

The author of Psychrometrics package acknowledges Professor Brent Stephens, Ph.D. from the Illinois Institute of Technology for kindly suggesting the source reference for equations used in this package.